The use of wireless communication devices such as telephones, pagers, personal digital assistants, laptop computers, etc., hereinafter referred to collectively as “mobile appliances” or “mobiles stations” has become prevalent in today's society. In recent years, at the urging of public safety groups, there has been increased interest in technology which can determine the geographic position or “geo-locate” a mobile station in certain circumstances.
Estimating the location of a mobile station may require one or more types of calibration data associated with the mobile station (e.g., signal strength, round trip time, time difference of arrival (TDOA), ground truth data, etc.). Determining precise ground truth measurements is important when generating an accurate calibration database. Without accurate ground truth information, the calibration database will contain significant errors which will in turn be reflected by poor location estimates. Any device used to retrieve ground truth data may produce some degree of signal degradation or drop-out. In the case of a GPS receiver used to collect ground truth data, degradation or drop-out could occur, for example, due to poor satellite visibility or high dilution of precision (DOP).
Referring to FIG. 1, a vehicle 40 may be configured with a collection device 45 to collect calibration data. Once calibration data has been obtained, it may be stored locally in an internal memory of the collection device 45, or the data may be transmitted to a receiving base station 60, where the data is stored in a calibration database 50.
The vehicle 40 may include a dead-reckoning device (not shown) to collect data during periods of signal degradation or drop-out. Such devices attempt to calculate the location of the vehicle when GPS location signaling obtained from a GPS satellite 70 becomes unavailable. Dead reckoning operates by estimating a location of a moving vehicle 40 using information, such as, but not limited to, the last accurate GPS location, velocity of the vehicle 40 and may include other known information.
Dead reckoning schemes often produce data results that may be unsatisfactory when attempting to perform a location estimate. FIG. 2 illustrates an exemplary dead reckoning operation. Referring to FIG. 2, a vehicle's estimated position is illustrated by the line (T) along the street. During a dead reckoning operation, there may be an increased chance of location error and the vehicle's estimated position (T) may be erroneous with respect to the actual position of the vehicle.
Current collection procedures utilized to generate a calibration database 50 may also be laborious, time-consuming and expensive. Simplifying the test and measurement equipment (T&M) needed, and the procedures for obtaining calibration data may save time and expenses.
To increase the accuracy of location estimates, it is important the collected calibration data be as precise as possible. To ensure the integrity of the calibration data after it has been collected, a data modification and/or data replacement algorithm may be implemented to enhance the accuracy of the collected data. Enhancing the collected calibration data may reduce the chances of errors occurring during a subsequent location process. Additionally, generating a calibration database using enhanced collection procedures may simplify the collection process.
One embodiment of the present subject matter is a method for generating a calibration database that may be used to locate a mobile station. The method may include obtaining location data from a plurality of geographic locations within a region and providing a location information database which includes latitude and longitude information fore each of a plurality of points within the region. The method may also include determining two points in proximity to one of the plural geographic locations, interpolating between the two points to determine a third point, and entering the location of the third point in the calibration database.
Another embodiment of the present subject matter is method for generating a calibration database employing a wireless device in a region that contains plural streets and intersections of the plural streets. The method may include obtaining location data of a plurality of geographic locations situated within a region from the wireless device and providing a location information database including latitude and longitude information for each of a plurality of points within the region. The method may also include determining a status of the wireless device, determining from the status a most likely street the wireless device is located for a first one of the plural geographic locations, and determining a first point of the plural points that is in proximity to said first geographic location. The method may then enter the first point in the calibration database.
Another embodiment of the present subject matter is a system for generating a calibration database. The system may include a first database containing location data obtained at a plurality of geographic locations within a region and a location information database which includes latitude and longitude information for each of a plurality of points in the same region. The system may also include circuitry for determining points in the location information database that are in proximity to a geographical location, circuitry for interpolating between the points to determine a third point, and circuitry for entering the third point in the calibration database.
Another embodiment of the disclosed subject matter is a system for generating a calibration database in a region with plural streets and intersections using a wireless device. The system may include a wireless device for obtaining location data at geographic locations within a region and a location information database that includes latitude and longitude information for a plurality of points within the region. The system may also include circuitry for determining a status of the wireless device, circuitry for determining from the status which street the wireless device is situated upon for a geographic location, circuitry for determining a first point proximate to the geographic location, and circuitry for entering the first point in the calibration database.
These and other advantages of the disclosed subject matter over the prior art will be readily apparent to one skilled in the art to which the disclosure pertains from a perusal of the claims, the appended drawings, and the following detailed description of the preferred embodiments.